The Joubert syndrome protein ARL13B binds tubulin to maintain uniform distribution of proteins along the ciliary membrane
The Joubert syndrome protein ARL13B binds tubulin to maintain uniform distribution of proteins along the ciliary membrane
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DOI：
10.1242/jcs.212324
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发表时间：
2018-05-01
影响因子：
4
通讯作者：
Iomini, Carlo
中科院分区：
文献类型：
--
作者：
Revenkova, Ekaterina;Liu, Qing;Iomini, Carlo
纤毛介导的信号转导涉及所选分子沿纤毛膜沿着的精确靶向和定位。然而，这些事件背后的分子机制尚不清楚。Joubert综合征蛋白ARL 13 B是一种膜相关G蛋白，其定位于沿着纤毛并在蛋白质转运和信号传导中起作用。我们确定微管蛋白作为一个直接的相互作用的ARL 13 B，并表明，协会发生通过G-结构域和独立于GTdR活性的ARL 13 B。G-结构域是ARL 13 B与轴丝在体外和体内相互作用所必需的。我们进一步表明，缺乏微管蛋白结合G结构域（ARL 13 B-Delta GD）或其GT3结构域失活（ARL 13 B-T35 N）的外源表达突变体保留纤毛定位，但未能挽救空Arl 13 b（hnn）小鼠胚胎成纤维细胞（MEFs）的纤毛发生缺陷。然而，虽然ARL 13 B-Delta GD和膜蛋白Smoothened（SMO）和生长抑素受体-3（SSTR 3）沿着Arl 13 b（hnn）MEF的纤毛不均匀地分布，但ARL 13 B-T35 N沿着纤毛均匀地分布，并使SMO和SSTR 3均匀分布。因此，我们提出了一个迄今未知的功能ARL 13 B在锚定睫状膜蛋白的轴丝通过直接相互作用的G-结构域与微管蛋白。
Cilia-mediated signal transduction involves precise targeting and localization of selected molecules along the ciliary membrane. However, the molecular mechanism underlying these events is unclear. The Joubert syndrome protein ARL13B is a membrane-associated G-protein that localizes along the cilium and functions in protein transport and signaling. We identify tubulin as a direct interactor of ARL13B and demonstrate that the association occurs via the G-domain and independently from the GTPase activity of ARL13B. The G-domain is necessary for the interaction of ARL13B with the axoneme both in vitro and in vivo. We further show that exogenously expressed mutants lacking the tubulin-binding G-domain (ARL13B-Delta GD) or whose GTPase domain is inactivated (ARL13B-T35N) retain ciliary localization, but fail to rescue ciliogenesis defects of null Arl13b(hnn) mouse embryonic fibroblasts (MEFs). However, while ARL13B-Delta GD and the membrane proteins Smoothened (SMO) and Somatostatin receptor-3 (SSTR3) distribute unevenly along the cilium of Arl13b(hnn) MEFs, ARL13B-T35N distributes evenly along the cilium and enables the uniform distribution of SMO and SSTR3. Thus, we propose a so far unknown function of ARL13B in anchoring ciliary membrane proteins to the axoneme through the direct interaction of its G-domain with tubulin.